The present invention relates to a metal-laminate type gasket, such as a cylinder head gasket installed between two members for sealing, such as a cylinder head and a cylinder block and the like. More specifically, the metal-laminate type gasket is formed of more than three metal plates, wherein two of the metal plates are connected together.
In a state that the cylinder head gasket is sandwiched between the cylinder head and the cylinder block (cylinder body) of an engine for an automobile, the cylinder head gasket is tightened by head bolts to seal fluids, such as fuel gas, oil, cooling water and the like.
In a metal-laminate type gasket laminating a plurality of metal plates of the cylinder head gasket, as a method for connecting two plates at a local connecting portion, there is proposed a method in which a claw portion formed in a metal constituting plate is inserted into a fixation hole in the other metal constituting plate to thereby engage the claw portion to a periphery of the fixation holes.
One of the methods, a steel laminate gasket is provided, which is formed of a metal plate provided with hems or flanges constituting hole sealing portions around a plurality of openings constituting combustion chamber holes, and a metal plate provided with notch portions between the openings adjacent to each other by providing to partially overlap the plurality of openings constituting the combustion chamber hole. In the steel laminate gasket, notch holes (fixation holes) are formed between the openings adjacent to each other in the metal plate having no notch portion, and the metal plate with notch portions includes projection portions (claw portions) facing each other. The projection portion (claw portion) is inserted into the notch hole to be engaged (for example, Japanese Utility Model Publication No. 05-59050).
In order to connect two plates with a simple structure and furthermore to facilitate the connecting operation, the metal-laminate type gasket laminating two metal plates includes, at a proper position of the inner surface of a metal-laminate type gasket, includes a tongue piece (claw portion) in one of the two plates by cutting a part of the plate, and a fixation hole for inserting the tongue piece in the other plate. The tongue piece in the one of the two plates is inserted through the fixation hole in the other plate to thereby project toward the other side. Thus, the tongue piece is engaged to the periphery of the fixation hole so that the two laminated plates are fixed each other (for example, Japanese Utility Model Publication No. 06-20955).
However, when the connecting method described above is employed, a thickness of the local connecting portion is increased from the periphery portion with the amount of the tongue piece engaging the periphery of the fixation hole.
Also, recently, in a metal-laminate type gasket laminating a plurality of metal plates, the two plates are connected at a local connecting portion by laser or spot welding. Even though this method is employed, a thickness of the local connecting portion is made greater than that of the periphery portion.
In a state that the thickness of the local connecting portion is increased, when a connecting force is applied between the two members located both sides of the metal-laminate type gasket, a significant high surface pressure is locally generated at the portion where the thickness is locally increased.
Consequently, it can be considered that a third metal plate covers the connecting portion of the two metal plates to thereby disperse the surface pressure. However, when a strong connecting force is applied between engine members, the portion where the thickness is increased abuts against the third metal plate to thereby locally generate a significant high surface pressure at the portion.
Therefore, there has been a problem that the position of the local connecting portion is required to be limited to a portion where sealing property is not affected by the high surface pressure generated, i.e. both ends of the gasket where it is unrelated to sealing or a water jacket portion or the like.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a metal-laminate type gasket formed of more than three metal plates, wherein two of the metal plates, i.e. a first and a second metal plates, are connected at a local connecting portion. In the metal-laminate type gasket, an increase of local surface pressure can be prevented from generating at the connecting portion.